ABSTRACT
Infections in the bones, joints and muscles are acute, chronic or granulomatous. Granulomatous infection is a ‘catch all’ term used to describe evidence of prior or inactive infection that results in the formation of granulomas which wall off the substances that the immune system perceives as foreign but is unable to eliminate. In histological terms, an important feature of granulomas is whether or not they contain necrosis (mass of dead cells without nuclei). The presence of necrosis indicates that the granuloma has an infective cause. Two types of necrosis have been identified – caseous, which describes the appearance as being ‘cheese-like’, and non-caseous. In the musculoskeletal system, caseous necrosis usually indicates the presence of tuberculosis (TB). Other infections characterized by granulomas include histoplasmosis, cryptococcosis, coccidiomycosis, blastomycosis, leprosy and cat scratch disease. Non-infectious causes of granulomas include sarcoidosis, Crohn disease, Wegener disease, Churg-Strauss syndrome and pulmonary rheumatoid nodules.
